javascript-tutorials/async-await/event-loop.md

JavaScript is single-threaded but it can still take advantage of asynchronous programming.

The Event Loop is a Javascript construct responsible for holding operations to be executed asynchronously with respect to the main flow of execution. Whenever we meet a portion of code that may not be possible to execute now, it is put in the Event Loop. Let's look at some examples:

  setTimeout(() => console.log('test'), 1000);

console.log('test') will be put in the Event Loop.

  const promise = new Promise(function (resolve, reject) {
  console.log('test');
  resolve();
}).then(() => {
  console.log('test2');
});

console.log('test2') will be put in the Event Loop.